EXPLANATION OF THE SEA-SERPENT MAGNETIC STRUCTURE OF SUNSPOT PENUMBRAE
- Center for Turbulence Research, Stanford University, Stanford, CA 94305 (United States)
- Instituto de Astrofisica de AndalucIa (CSIC), Apdo. de Correos 3004, E-18080 Granada (Spain)
- NORDITA, Department of Astronomy, AlbaNova University Center, SE 10691 Stockholm (Sweden)
- NASA Ames Research Center, Moffett Field, Mountain View, CA 94040 (United States)
Recent spectro-polarimetric observations of a sunspot showed the formation of bipolar magnetic patches in the mid-penumbra and their propagation toward the outer penumbral boundary. The observations were interpreted as being caused by sea-serpent magnetic fields near the solar surface. In this Letter, we develop a three-dimensional radiative MHD numerical model to explain the sea-serpent structure and the wave-like behavior of the penumbral magnetic field lines. The simulations reproduce the observed behavior, suggesting that the sea-serpent phenomenon is a consequence of magnetoconvection in a strongly inclined magnetic field. It involves several physical processes: filamentary structurization, high-speed overturning convective motions in strong, almost horizontal magnetic fields with partially frozen field lines, and traveling convective waves. The results demonstrate a correlation of the bipolar magnetic patches with high-speed Evershed downflows in the penumbra. This is the first time that a three-dimensional numerical model of the penumbra results in downward-directed magnetic fields, an essential ingredient of sunspot penumbrae that has eluded explanation until now.
- OSTI ID:
- 21451073
- Journal Information:
- Astrophysical Journal Letters, Vol. 716, Issue 2; Other Information: DOI: 10.1088/2041-8205/716/2/L181; ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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